1. Field of the Invention
The present invention relates to an optical sensor to be used in detection of a chromogenic reaction of an object of measurement.
2. Description of the Related Art
As concentration measuring methods for measurement objects such as varieties of hormones, such as insulin, proteins, or glycemia, there can be taken the following methods as examples. For instance, among others, there is such a method that makes a measurement of a voltage developed in an electrode reaction, and an optical concentration measuring method that uses a pigment to be absorbed by reaction with a substance to measure its chromatic change in terms of a change in quantity of light such as laser light. Among those, the optical concentration measuring method is advantageous in that it provides a measurement with high degradation ability.
The optical concentration measuring method employs a sensor chip for holding a measurement object during a measurement, as well as for wave-guiding a beam of laser light. FIG. 8 is a simple illustration for explanation of an exemplary sensor chip. As illustrated in FIG. 8, the sensor chip 100 is configured with a glass chip 101 for wave-guiding a beam of laser light, a pair of gratings 102a and 102b provided on the glass chip 101 for changing directions of rays of laser light having income to the sensor chip 100, and a measuring region 103 for a measurement object S to be held thereon.
Brief description of the optical concentration measuring method follows. First, a liquid measurement object S is injected inside the measuring region 103, and for instance a pigment is reacted with the measurement object S for adaptation to absorb incident light in accordance with concentration of the measurement object S. After that, rays of laser light are guided inside the glass chip 101 as illustrated in FIG. 8, and those rays of laser light having come through the measuring region 103, where the measurement object S was injected, are taken outside the glass chip 101 to detect the light quantity. From a detected value of light quantity, a concentration of the measurement object S is estimated.
For measurements of concentration using the optical concentration measuring method, it is required to prevent a liquid measurement object from flowing on a glass chip or the like. Hence, the measurement object is dropped in a region opened simply at the upside like the measuring region 103 as illustrated in FIG. 8 for instance, where the measurement object is held for measurement.
Further, there has been disclosed also a method in which a specimen is brought into direct contract with a meshed conductive thin-film side of an optical waveguide type glucose sensor, while making the concentration measurement, like an invention described in Japanese Patent Application Laying-Open Publication No. 2004-212188. For this invention, for instance a pulsing electric field is applied to the specimen, to sample a biologic fluid containing glucose as a measurement object from the specimen.